1. Field of the Invention
The present invention relates to a traction drive speed reducer including a circumscribed axis, a plurality of intermediate axes arranged contacting around the outer periphery of the circumscribed axis, and an inscribed cylinder inscribing the outer periphery of the intermediate axis.
The present invention also relates to a conveyance apparatus using, as a drive apparatus, a traction drive speed reducer including a circumscribed axis, a plurality of intermediate axes arranged contacting around the outer periphery of the circumscribed axis, and an inscribed cylinder inscribing the outer periphery of the intermediate axes.
The present invention also relates to an arrangement of the 2-axis output encoder in an conveyance apparatus.
2. Related Art
(1) In a traction drive speed reducer including a circumscribed axis, a plurality of intermediate axes arranged contacting around the outer periphery of the circumscribed axis, and an inscribed cylinder inscribing the outer periphery of the intermediate axes, the traction drive speed reducer in which the rotation of the drive motor is inputted into the circumscribed axis, and the intermediate axes is rotatably supported by the supporting member, and the output is taken from the supporting member, is well known (for example, JP-A-58-119746).
However, in the conventionally well known traction drive speed reducer, when there is a dispersion in the diameter of a plurality of intermediate axes, the rotation center of the supporting member from which the output is taken out can not corresponds with the center of the circumscribed axis. Therefore, the nonuniformity of the rotation occurs in the output taken from the supporting member, which is disadvantageous.
That is, in the conventional traction drive speed reducer, the rotation force from the drive motor is inputted into the circumscribed axis, in contrast to that, the output is taken from the supporting member supporting the intermediate axes. In this case, when the center of the inscribed cylinder is dislocated due to the dispersion of the diameter of a plurality of intermediate axes, the rotation center of the output is rotated around the original rotation center with the radius corresponding to the dislocated amount, therefore, the rotation of the output side causes the variation due to the dislocation of the rotation center.
Accordingly, an object of the present invention is to provide a traction drive speed reducer free from the afore-mentioned problem.
(2) In a field in which a fine processing inhibiting a particle, such as in a semiconductor wafer, or LCD (liquid crystal display) glass base, is necessary, the conveyed material can not be conveyed (can not hold) by chucking (grasp the conveyed material). Therefore, as the handling method in such the conveyance field, it is the present condition that the conveyance is conducted by a conveyance apparatus of a system in which the conveyed material is only put (only supported) on the hand (end effector) section.
However, in such the conveyance apparatus, in the support, there are an organic (such as the rubber, or the like) support, and an inorganic (ceramic, or the like) support, and there is a problem that, although the organic support has the comparatively large frictional force, it can not be used in the high temperature portion. Further, there is a vacuum absorption system, however, although it can be used in the air, it can not be used in the vacuum which is desirably used at the time of processing of the semiconductor wafer, or the LCD (liquid crystal display) glass base. Further, in the vacuum absorption method, the structure is complicated and the cost is high.
Accordingly, in many cases, the conveyed material (wafer, or the like) is held only by the frictional force with the hand support section. However, when such the conveyed material is suddenly moved, or moved while being vibrated, the conveyed material is slid and dislocation is caused, and the disadvantages such as the generation of the particle positioning failure, and the damage of the conveyed material, occur. Therefore, for the conveyance apparatus used in such the accurate conveyance field, the conveyance apparatus by which the conveyance with the extremely small vibration (acceleration) can be conducted (smooth conveyance), is required.
In such the conveyance apparatus in which the particle is inhibited and the fine processing is necessary, such as the semiconductor wafer or LCD (liquid crystal display) glass base, conventionally the direct drive (DD) system drive apparatus is used (JP-A-3-281183). However, in the DD system drive apparatus, because the output density (torque/volume, torque/motor capacity) is small, there is a problem that the drive apparatus is large, and the power source capacity becomes also large.
On the one hand, in order to aim at the compactification of the drive apparatus, there is also a conveyance apparatus using a speed reducer having a gear mechanism. By using the speed reducer having the gear mechanism, the compactification of the drive apparatus can be possible. However, because the gear is provided, there is a problem that the backlash exists, or vibration or noise is generated. Further, in order to reduce the vibration or noise, in the conveyance apparatus using the speed reducer having the gear mechanism, the control becomes complicated, and the cost is high.
Accordingly, another object of the present invention is to provide a conveyance apparatus by which the problems accompanied to the above conventional technology can be solved, and by which the traction drive speed reducer is used for the drive apparatus, and a compact and low vibrationxe2x80xa2low noise conveyance apparatus by which the semiconductor wafer or LCD (liquid crystal display) glass base is processed.
(3) In the conveyance apparatus used in a field which inhibits a particle and requires an accurate processing, such as a semiconductor wafer or LCD (liquid crystal display) glass base, it is well-known that an optical encoder is arranged in the vacuum (for example, JP-W-8-506771 (U.S. Pat. No. 5,720,590)).
In the conveyance apparatus disclosed in this JP-W-8-506771, because an encoder or bearing is provided in the vacuum atmosphere, the use of the high cost encoder or bearing for the vacuum atmosphere specification is necessary. Further, because the bearing is used in the vacuum atmosphere, when the load capacity is desired to be increased, it is a cause of the particle generation, therefore, there is a problem that the load capacity can not be increased.
Accordingly, yet another object of the present invention is to provide an arrangement of a 2-axis output encoder in a simply structured conveyance apparatus.
According to a first aspect of the invention, the problems accompanied to the conventional art is solved by a traction drive speed reducer which comprises a circumscribed axis, a plurality of intermediate axes arranged contacting around the outer periphery of the circumscribed axis, and an inscribed cylinder inscribing the outer periphery of the intermediate axes, wherein a supporting member to rotatably support the intermediate axes is fixed, a drive motor is connected to at least one of the plurality of intermediate axes, and an output is taken from the circumscribed axis having the larger diameter than the outer diameter of the intermediate axis.
In the present invention, the rotation is inputted into the intermediate axis, and the output is taken from the circumscribed axis located at the center. That is, the output axis which is the circumscribed axis, is set at the rotation center of the reference output, and the supporting member is fixed. According to this structure, even when there is the dispersion of the diameter in a plurality of intermediate axes, because the inscribed cylinder which is a free condition, allows the deformation due to the dispersion of the diameter of the intermediate axes, its rotation center is simultaneously dislocated. As the result, the variation of the rotation due to dispersion of the diameter of a plurality of intermediate axes is not generated in the circumscribed axis as the output axis.
Further, the present invention can be applied also in the case where a plurality of coaxial outputs are necessary. That is, when a traction drive speed reducer is structured in such a manner that, in a traction drive speed reducer which comprises a circumscribed axis, a plurality of intermediate axes arranged around the outer periphery of the circumscribed axis, and an inscribed cylinder inscribing the outer periphery of the intermediate axes, the traction drive speed reducer is characterized in that: more than two circumscribed axes are arranged coaxially; respective plurality of intermediate axes are arranged contacting around the outer periphery of respective circumscribed axes; a supporting member to rotatably support the respective intermediate axes is fixed; and the rotation is respectively inputted into at least one of paired intermediate axes, and the output is taken from the corresponding circumscribed axes, and more than two coaxial outputs can be taken out, then, the output without rotation variation can be taken from coaxial output axes. Particularly, the traction drive speed reducer having such the output axes has the very excellent characteristics, for example, as the drive mechanism of the drive section of the industrial robot.
According to a second aspect of the present invention, an conveyance apparatus which is comprising a drive motor, a drive arm driven by the drive motor, and a conveyance table connected to a top end of the drive arm, wherein an output from the drive motor is transmitted to the drive arm through a traction drive speed reducer comprising the circumscribed axis, a plurality of intermediate axes arranged around the outer periphery of the circumscribed axis, and an inscribed cylinder inscribing the outer periphery of the intermediate axes, is provided.
According to the conveyance apparatus of the present invention, the drive apparatus can be compact, and by using a traction drive system in which the speed reducer has no gear, the drive can be smooth and the vibration or noise can be reduced, and the conveyance can be conducted without generating the dislocation of the conveyed material. Because, by using the traction drive speed reducer, there is no backlash (play), and there is no impact due to the play at the time of the drive start, thereby, the dislocation of the conveyed material is not caused.
In the present invention, the conveyance apparatus can be made to be an apparatus having two coaxially arranged output axes, wherein each output axis is connected to a corresponding drive motor through the traction drive speed reducer comprising the circumscribed axis, a plurality of intermediate axes arranged around the outer periphery of the circumscribed axis, and inscribed cylinder inscribing the outer periphery of the intermediate axes, and two coaxial outputs can be taken from the two coaxial output axes.
In this case, two coaxially arranged output axes of the conveyance apparatus and an output member of the traction drive speed reducer may be integrally connected with each other, or may be connected through a transmission member such as an endless belt.
The traction drive speed reducer may fix a carrier which rotatably supports a plurality of inter mediate axes, and input the rotation from at least one of paired intermediate axes, and take out the output from the corresponding circumscribed axis, or it may input the rotation from the circumscribed axis and fix an inscribed cylinder which is inscribed by the plurality of the intermediate axes, and take out the rotation output from the carrier which rotatably supports the plurality of intermediate axes.
Further, when the conveyance apparatus of the present invention is structured in such a manner that the front stage speed reducer is connected with the front stage of the traction drive speed reducer, wherein the front stage speed reducer is constructed by the traction drive speed reducer comprising the circumscribed axis, a plurality of intermediate axes arranged around the outer periphery of the circumscribed axis, and inscribed cylinder inscribing the outer periphery of the intermediate axes, the speed reduction ratio is further increased, and there is no backlash (play), thereby, there is no impact due to the play at the start of the drive, and it is more preferable in order that the dislocation of the conveyed material may not be caused.
Further, in the present invention, the conveyance apparatus may be characterized in that the position detector is provided on the output side of the traction drive speed reducer. In the traction drive system, in its structure, it is considered that the minute slide is caused inside the traction drive. Therefore, when it is structured such that the position detector is provided on the output side, even when the slide is caused in the traction drive speed reducer, the rotation position of the output side can be detected by the position detector, thereby it can be appropriately recovered and corrected.
Further, in the present invention, it is preferable that the conveyance apparatus is characterized in that an interference is set by making the sum of the outer diameter of the circumscribed axis and two times of the outer diameter of the intermediate axis, to be not smaller than the inner diameter of the inscribed cylinder, and the torque adjusting function is provided by the interference. In the present invention, the traction drive speed reducer is used, and even when the arm of the conveyance apparatus collides with any material by any possibility, because it can be avoided by generating a slide, the conveyance apparatus is not damaged as in the case of the speed reducer using the gear. Further, when the position detector is provided as described above, it can be easily restored. In addition to that, as described above, by structuring such that an interference is set by making the sum of the outer diameter of the circumscribed axis and two times of the outer diameter of the intermediate axis, to be not smaller than the inner diameter of the inscribed cylinder, because the torque can be adjusted by the interference, thereby, the anti-collision load can be easily set.
According to a third aspect of the invention, the above object is attained by structuring the system in such a manner that, in a conveyance apparatus for conveying a material to be conveyed by driving motors which are connected to each of output axes which are two coaxial axes of an inner axis and a hollow outer axis, and which are independently driven, an arrangement of 2-axis output encoder in the conveyance apparatus is characterized in that: axis seals exist between the inner axis and the outer axis, and between the outer axis and a cylindrical housing; a traction drive speed reducer structured by the drive motors and circumscribed axes, intermediate axes and inscribed cylinders, and for speed-reducing the rotation of the drive motor, is arranged on the air side; and position detectors of the inner axis penetrate through the speed reducer, and position detectors of the outer axis are arranged among the axis seal and the speed reducers, and provided on the air side.
The present invention is a conveyance apparatus which is particularly made to be a coaxial two-axis arrangement. Because the output axis encoder, in the case of a magnetic type, has a possibility that a mis-operation is caused due to frictional powders (iron powders) generated from the speed reducer, it can not be arranged in oil (the same atmosphere as the speed reducer). Thereby, the output axis encoder should be arranged in the air and oil-less atmosphere. However, in the coaxial two-axis, the two-axis can not be arranged in the same position. This is because it is necessary that the receiving sensor is arranged on the fixed portion, however, particularly on the inner axis side output axis, there is the outer axis output axis (rotation axis) and further also the speed reducer in the outside, therefore, there is no fixing position. According to this problem, it is necessary that the axis of the inner axis side encoder is necessarily extended to the opposite direction to the output side, and extended to the fixed position, however, normally, on the reversal side of the output side, there is the speed reducer or motor, and when it is made to be hollow and penetrated, the structure also becomes complicated, thereby, the drive apparatus cannot also be compact. (The encoder should be arranged below the motor.) In contrast to this, as in the present invention, when the traction drive structure is applied, the first stage traction drive and the motor can be arranged to be offset, and the first stage traction drive and the motor and the inner axis side output encoder can be arranged in parallel to each other. Thereby, the compactification can be obtained. In this connection, in this case, as described in the second aspect, the inner axis drive motor and the outer axis drive motor are parallelly arranged, and the inner axis position detector is positioned above the lower end surface of both drive motors, that is, in the arrangement space of both drive motors. Further, the first stage traction drive may be appropriately neglected.
As described above, it is problem for the durability or the instrument cost that the output axis encoder is arranged in the vacuum atmosphere. Particularly, in the case of the magnetic type, because the sensor side cannot endure the vacuum atmosphere, it can not be arranged in the vacuum. In contrast to this, in the present invention, because the position detector is arranged in the air side, and further, it is provided out of the oil lubrication portion of the speed reducer, the two-axis output encoder in the conveyance apparatus can be low costly and easily arranged.
In the present invention, it is preferable that the position detector of the inner axis and the outer axis is made to be the magnetic type. The cost of the magnetic type position detector is lower than that of the optical type position detector.
The present disclosure relates to the subject matter contained in Japanese patent application Nos. 2000-2090005 (filed on Jul. 10, 2000), 2000-251607 (filed on Aug. 22, 2000) and 2000-280763 (filed on Sep. 14, 2000), which are expressly incorporated herein by reference in their entirety.